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This is the first entry in the ExoMars 2016 Test Campaign Journal, a series of articles covering the main events during the development, integration and testing of the Trace Gas Orbiter (TGO) and the Entry, Descent and Landing Demonstrator Module (EDM). The Structural Model (SM) of the EDM has been delivered to ESA's European Space Research and Technology Centre (ESTEC) in Noordwijk, the Netherlands and some of the qualification testing has been performed.

The EDM arrived at ESTEC in mid-February, having been transported by road from the Turin facility of Thales Alenia Space, where it was integrated. Upon arrival in the loading bay, the transport container was cleaned and moved into an adjacent cleanroom. Once the container and its contents had reached thermal equilibrium with the surroundings, the container was opened. After checking the shock monitors in the container to ensure that the contents had not been subjected to any unexpected impacts during transport, the EDM was lifted from the container by crane and installed on its ground handling trolley. There the EDM was subjected to a leak-test, to verify the performance of the bio-seal between its main structural elements, the aeroshell, front shield and back cover.

Views of the ExoMars EDM structural model on the multishaker (left and top right) and QUAD shaker for vibration testing. Credit: ESA.

After having been moved to the Vibration Area, the EDM has now undergone a series of vibration tests on the ESTEC Test Centre Multishaker (Y- and Z-axes) and the Quad Shaker (X-axis [flight direction]).

The Multishaker consists of a slip table, onto which the spacecraft under test is mounted, and a pair of 160 kN electrodynamic exciters that vibrate the table and spacecraft. The Multishaker is capable of producing sinusoidal accelerations of up to 19 g with a test item mass of up to 10 000 kg and can operate over the frequency range 3 Hz to 2 kHz.

The QUAD shaker is the most powerful electrodynamic shaker at ESTEC and consists of a 3.3x3.3-metre magnesium alloy 'head expander' or table, fitted on top of four 160 kN electrodynamic exciters that move the table up and down. The QUAD shaker is capable of producing sinusoidal accelerations of up to 20 g with a test item mass of up to 10 000 kg and can operate over the frequency range 3 Hz to 2 kHz.

The EDM was subjected to swept-sine vibrations over a range from 5 Hz to 2 kHz along all three axes. The spacecraft was fitted with accelerometers to monitor the vibration of important structural components. Low-level sweeps were conducted to detect any unexpected mechanical characteristics that might lead to damage at higher vibration levels. Once these had been successfully completed, tests were performed at qualification levels from 5 Hz to 100 Hz, with notch filtering being applied at the critical frequencies to avoid excessive excitation.

The purpose of these tests is to qualify the spacecraft design by ensuring that it will be able to withstand the rigours of the mechanical environment it will experience during its launch on a Proton rocket.

The SM consists of all the structural components of the spacecraft, with the instruments, electronics boxes and other non-structural hardware represented by mass dummies. It is 2.4 m in diameter, 1.8 m high and weighs about 600 kg.

Upon completion of the vibration tests another leak test was performed, which demonstrated that the bio-seal performance had not been degraded by the mechanical loads of the vibration test campaign.

Following this testing at ESTEC, the EDM SM has been transported back to the Turin factory, where it will be used for further structural testing, namely the static Entry Load Test, and the Parachute Pull Test. These tests, which are scheduled to begin mid May this year, will demonstrate the structural capabilities of the EDM when subjected to entry into the Martian atmosphere and the deployment of its parachutes.

About the ExoMars 2016 Mission

The first mission of the ExoMars programme, which is scheduled to arrive at Mars in 2016, consists of a Trace Gas Orbiter (TGO) and an Entry, Descent and Landing Demonstrator Module (EDM). The main objectives of this mission are to search for evidence of methane and other trace atmospheric gases that could indicate active biological or geological processes and to test key landing technologies in preparation for ESA's contribution to subsequent missions to Mars.

The ExoMars 2016 mission is led by ESA, with partner Roscosmos supplying the launcher and instruments for the TGO science payload. The Prime Contractors are Thales Alenia Space (Italy) for the overall spacecraft and the EDM, while the TGO is being build by Thales Alenia Space (France) together with Co-Prime OHB (Germany).